Satellite communication systems typically have employed large aperture antennas and high power transmitters for establishing an uplink to the satellite. Recently, however, very small aperture antenna ground terminals, referred to as remote ground terminals, have been developed for data transmission at low rates. In such systems, the remote ground terminals are utilized for communicating via a satellite from a remote location to a central hub station. The central hub station communicates with multiple remote ground terminals, and has a significantly larger antenna, as well as a significantly larger power output capability than any of the remote ground terminals.
Typically, the remote ground terminals comprise a small aperture directional antenna for receiving and transmitting signals to a satellite, an outdoor unit mounted proximate the antenna which comprises a transmitter for producing and transmitting a modulated data signal and an indoor unit which demodulates incoming signals and also operates as an interface between a specific user's communication equipment and the outdoor unit.
The installation of such remote ground terminals entails positioning the directional antenna in the direction of the desired satellite so as to maximize the amplitude of the signal received from the satellite. Various techniques have been utilized to aim the antenna. One known technique is to couple a spectrum analyzer to the output of the demodulator of the indoor unit. The amplitude of the received signal is then monitored as the antenna position is adjusted. However, this technique has several drawbacks. First, it requires the use of additional equipment (i.e., the spectrum analyzer). Second, as the antenna is not located proximate the indoor unit, it requires the presence of two technicians to preform the installation.
U.S. Pat. No. 4,881,081 discloses a device for adjusting the antenna orientation which eliminates the need for two installation technicians. However, the device requires a substantial number of additional components which are dedicated exclusively for the purpose of antenna orientation.
Furthermore, the above devices typically operate as single carrier receivers (i.e., designed to receive a carrier signal having a single, predefined frequency) and therefore utilize a narrow band receiver to produce a narrow band intermediate frequency "IF" signal. The amplitude of the narrow band IF signal is then monitored as the position of the antenna is adjusted. The antenna is positioned correctly when the amplitude of the IF signal is the maximum obtainable value.
However, in systems which provide for a wide band IF signal, such as those capable of receiving multiple carrier frequencies, the foregoing methods are inadequate because the difference in the amplitude of the IF signal and the wide-band background noise output by the wide-band demodulator (i.e., the signal to noise ratio) is insufficient to allow the installer to readily determine when the antenna is pointed correctly. In other words, when monitoring the IF signal with a device such as a voltmeter, the background noise essentially masks the IF signal.
Accordingly, there exists a need for an apparatus and method for adjusting the antenna position of a remote ground terminal in systems providing for a wide band IF signal, which can be performed by a single technician and which does not require the use of additional components or equipment to perform the procedure.